Maintaining air quality in submarines is critical for crew health and operational effectiveness, especially during prolonged submerged missions. Traditional carbon dioxide (CO2) scrubbing systems rely on chemical absorbents like lithium hydroxide, but these methods have limitations in efficiency, weight, and regeneration. Nanofiber-based filtration systems present an advanced alternative, offering high surface area, tunable chemistry, and potential for integration into closed-loop life support systems. Military submarines, particularly those operated by navies with extended underwater endurance requirements, have stringent specifications for CO2 removal. These systems must operate reliably under variable humidity, pressure, and temperature conditions while minimizing power consumption and footprint.

Nanofiber membranes for CO2 capture leverage materials such as polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), or metal-organic framework (MOF)-embedded polymers. These fibers, typically 100-500 nm in diameter, provide a high surface-area-to-volume ratio, enhancing gas adsorption kinetics. Electrospinning is the primary fabrication method, allowing precise control over fiber morphology and composition. Functionalization with amine groups or incorporation of zeolitic imidazolate frameworks (ZIFs) improves selectivity for CO2 over other gases. For instance, amine-grafted PAN nanofibers demonstrate CO2 adsorption capacities of 1.5-2.0 mmol/g at 25°C and 1 atm, with regeneration achievable at 80-100°C.

Navy specifications for submarine CO2 scrubbing demand continuous operation with CO2 levels maintained below 0.5% by volume, per NATO STANAG 1411 standards. Systems must handle CO2 production rates of approximately 0.8-1.2 kg per crew member daily. Nanofiber scrubbers are evaluated for breakthrough time, pressure drop, and cyclic stability. Testing under simulated submarine conditions—humidity levels of 60-80% and temperatures of 15-30°C—shows that multilayer nanofiber filters achieve 90-95% CO2 capture efficiency at flow rates of 10-15 L/min per square meter of filter area. Pressure drop across these membranes is critical; values exceeding 50 Pa/cm² are typically rejected due to energy penalties in air circulation.

Closed-loop performance data from prototype systems indicate that nanofiber scrubbers can operate for 72-96 hours before requiring regeneration, depending on crew size and metabolic rates. Regeneration is accomplished through temperature or pressure swings, with some designs incorporating resistive heating directly into the nanofiber mats. Energy consumption for regeneration ranges from 0.8-1.2 kWh per kg of CO2 released, competitive with liquid amine systems but without corrosion risks. Long-term stability tests over 500 adsorption-desorption cycles show less than 10% degradation in capacity for MOF-composite nanofibers, meeting naval durability requirements.

Comparative analyses with granular activated carbon or pelletized sorbents highlight nanofiber advantages in weight and volume. A nanofiber module weighing 12 kg can replace a 25 kg lithium hydroxide canister system for the same crew size, critical in space-constrained submarines. Additionally, modular designs allow incremental replacement, avoiding full-system shutdowns during maintenance.

Challenges remain in scaling production to meet military procurement volumes and ensuring performance under extreme conditions, such as depth-charge shocks or rapid pressure changes. However, ongoing material advancements—such as graphene oxide-coated nanofibers for mechanical reinforcement and humidity-resistant MOFs—are addressing these limitations.

Integration with existing submarine environmental control systems requires minimal retrofitting, as nanofiber filters can interface with standard ducting and monitoring hardware. Real-time CO2 sensors coupled with predictive algorithms optimize regeneration cycles, further reducing energy use. Future developments may focus on hybrid systems combining nanofibers with photocatalytic layers for simultaneous CO2 conversion to harmless byproducts.

Nanofiber CO2 scrubbing represents a convergence of materials science and naval engineering, offering a path toward lighter, more efficient air revitalization for next-generation submarines. As underwater missions grow longer and more demanding, such innovations will be pivotal in maintaining crew safety and operational readiness without compromising stealth or endurance.